METHOD: The adapted multiple point stimulation (AMPS) method for calculating motor unit numbers (MUNE) was applied in 12 patients with amyotrophic lateral sclerosis (ALS) before riluzole therapy (T(0)) and again after 4, 8 and 12 months of treatment. RESULTS: Paired Student's t-test indicated a significant decrease of thenar MUNE and compound muscle action potential (CMAP) size at each 4-monthly interval, while average surface motor unit potential (SMUP) size did not change significantly over time. The rate of motor unit (MU) loss at month 4 was more than 20% in six patients (group 1) and less than 20% in six other patients (group 2). Comparison of groups 1 and 2 by Mann-Whitney U-testing indicated that percent changes in thenar MUNE and CMAP size compared to baseline were significantly different at months 4, 8 and 12, while no difference between the two groups was found for average SMUP size variations. In the group with a slow rate of MU loss, CMAP size remained stable, while in the group with a rapid rate of MU loss, there was a dramatic reduction in size of the CMAP. A positive correlation was found between percent change in thenar MUNE at T(4) and at T(12) (P < 0.001). CONCLUSION: AMPS is a useful technique to document MUNE, SMUP size and CMAP size changes over time in patients with ALS. [less ▲]

BACKGROUND AND PURPOSE: Prevalence and characteristics of ipsilateral upper limb motor-evoked potentials (MEPs) elicited by focal transcranial magnetic stimulation (TMS) were compared in healthy subjects and patients with acute stroke. METHODS: Sixteen healthy subjects and 25 patients with acute stroke underwent focal TMS at maximum stimulator output over motor and premotor cortices. If present, MEPs evoked in muscles ipsilateral to TMS were analyzed for latency, amplitude, shape, and center of gravity (ie, preferential coil location to elicit them). In stroke patients, possible relationships between early ipsilateral responses and functional outcome at 6 months were sought. RESULTS: With relaxed or slightly contracting target muscle, maximal TMS over the motor cortex failed to elicit ipsilateral MEPs in the first dorsal interosseous (FDI) or biceps of any of 16 normal subjects. In 5 of 8 healthy subjects tested, ipsilateral MEPs with latencies longer than contralateral MEPs were evoked in FDI muscle (in biceps, 6 of 8 subjects) during strong (>50% maximum) contraction of the target muscle. In 15 of 25 stroke patients, ipsilateral MEPs in the unaffected relaxed FDI (in biceps, 6 of 25 stroke patients) were evoked by stimulation of premotor areas of the affected hemisphere. Their latencies were shorter than those that MEPs evoked in the same muscle by stimulation of the motor cortex of the contralateral unaffected hemisphere. Such responses were never obtained in normal subjects and were mostly observed in patients with subcortical infarcts. Patients harboring these responses had slightly better bimanual dexterity after 6 months. CONCLUSIONS: Ipsilateral MEPs obtained in healthy individuals and stroke patients have different characteristics and probably different origins. In the former, they are probably conveyed via corticoreticulospinal or corticopropriospinal pathways, whereas in the latter, early ipsilateral MEPs could originate in hyperexcitable premotor areas. [less ▲]

Decrement of the thenar compound muscle action potentials (CMAP), after repetitive nerve stimulation (RNS) of the median nerve at 3 Hz, was evaluated in patients with ALS before riluzole therapy. CMAP size as well as motor unit number and size estimates were evaluated twice before and after 1 year of riluzole therapy. The correlation between decrement and CMAP size reduction per year was highly significant (r = 0.77), but no relationship could be demonstrated between decrement and other variables. The authors thus propose that decrement after RNS may be used as a predictor of further drop in CMAP size. [less ▲]

OBJECTIVES: Transcranial magnetic stimulation (TMS) was used to investigate motor cortex excitability, intracortical excitatory, and inhibitory pathways in 18 patients having experienced a first "grand mal" seizure within 48 hours of the electrophysiological test. All had normal brain MRI, and were free of any treatment, drug, or alcohol misuse. Results were compared with those of 35 age matched normal volunteers. METHODS: The following parameters of responses to TMS were measured: motor thresholds at rest and with voluntary contraction, amplitudes of responses, cortical silent periods, and responses to paired pulse stimulation with interstimulus intervals of 1 to 20 ms. RESULTS: In patients, there were significantly increased motor thresholds with normal amplitudes of motor evoked potentials (MEPs), suggesting decreased cortical excitability. Cortical silent periods were not significantly different from those of normal subjects. Paired TMS with short interstimulus intervals (1-5 ms) induced normal inhibition of test MEPs, suggesting preserved function of GABAergic intracortical inhibitory interneurons. On the contrary, the subsequent period of MEP facilitation found in normal subjects (ISIs of 6-20 ms) was markedly reduced in patients. This suggests the existence of abnormally prolonged intracortical inhibition or deficient intracortical excitation. In nine patients retested 2 to 4 weeks after the initial seizure, these abnormalities persisted, although to a lesser extent. CONCLUSION: The present findings together with abnormally high motor thresholds could represent protective mechanisms against the spread or recurrence of seizures. [less ▲]

BACKGROUND AND PURPOSE: Transcranial magnetic stimulation (TMS) has been proposed as a prognostic tool in stroke patients. Most of the previous studies agree in considering the presence of motor-evoked ... [more ▼]

BACKGROUND AND PURPOSE: Transcranial magnetic stimulation (TMS) has been proposed as a prognostic tool in stroke patients. Most of the previous studies agree in considering the presence of motor-evoked potentials (MEPs) in the first days after a stroke as an indicator of good outcome. In the present study, we have assessed the prognostic value of the absence of response to early TMS on hand motor recovery in stroke patients with complete hand palsy at onset due to ischemia in the area of the middle cerebral artery. METHODS: Fifteen patients submitted to TMS within 48 hours of stroke onset (defined as day 1) and again after 1 year. They were also evaluated clinically on day 1 by a scale derived from the Medical Research Council (MRC) and by the National Institutes of Health (NIH) stroke scale; they were reevaluated by the same scales and by Barthel Index on day 365. RESULTS: On day 1, all the patients had complete hand palsy and no response to TMS; their NIH scores showed great variability. After 1 year, 6 of 15 patients regained small and prolonged MEPs, together with a very poor and not functionally useful motor recovery. NIH scores were significantly improved. Barthel Index scores showed large interindividual differences and were not correlated with MRC scores. CONCLUSIONS: We conclude that in patients with complete hand palsy, the absence of response to TMS in the first hours is predictive of absent or very poor, not useful, hand motor recovery. [less ▲]